A pedestrian is clinging to life after he was struck by a double-decker tour bus Friday afternoon in the West Village, authorities said.

The victim, believed to be in his 50s, was crossing Sixth Avenue around 1:45 p.m. when he was caught under the bus as it was turning from West Fourth Street, police said.

Shaunte Service, who works nearby, ran to the scene when she heard screams.

“I ran out immediately to help him. I held his hand, I asked him his name, told him to breathe,” Service said. “I saw bone and flesh and blood. … I was just trying to help him get through this traumatic experience.”

First-responders rushed the unidentified man to Bellevue Hospital, where he is listed in critical condition.

The driver of the bus, which was full of tourists at the time of the collision, stayed at the scene.